The general goals of the project are to, a) Investigate the nature of neuropsychological impairments in children with neurofibromatosis, type I (NF), a genetic disorder with a high incidence of academic impairment and neuropathology; b) Investigate the underlying neuroanatomical basis of these impairments, and c) Determine the added contribution of the diagnosis of a brain tumor to the cognitive status of children with NF. Research will be directed towards 3 specific aims: 1) Identify domains of cognitive impairment in children with NF and determine how these patterns are associated with deficits in learning and academic achievement. 2) Determine the underlying anatomical basis of cognitive impairment. 3) Document the added effect of a diagnosis of brain tumor on neuropsychological functioning. Three groups will be studied in a cross-sectional design at a single timepoint: Children with NF only; children with NF pius a brain tumor; and normal healthy children. Data will be obtained from all study participants from two sources: a) Neuropsychological: A comprehensive battery of tests assessing intellectual, academic achievement, and cognitive functioning; b) Anatomical: MRI scans will undergo quantitative morphometric analyses to determine the location and volume of areas of high signal intensity commonly found in children with NF and the volume of cerebral white matter. Children who are between 6 and 12 years old at the time of enrollment will be eligible for the study which will requires years to complete. Wherever possible, depending on the nature of the hypothesis being evaluated, analyses will be multivariate, taking into account the multiple outcome measures used to evaluate a specific hypothesis. Qualitative indices from the neuroimaging domain will be analyzed using appropriate methods for categorical data analysis to examine group differences. Quantitative indices will be analyzed using MANOVA. Evaluating the neuroanatomical basis for cognitive deficits in NF will be accomplished using multiple regression and correlation. Knowledge from this study will provide information about cognitive impairments in children in general and suggest avenues of research into their biological bases and possibilities for their remediation.